John invited his mother over for dinner. During the meal, his mother couldn't help noticing how beautiful John's roommate Julie was. She had long been suspicious of a relationship between John and his roommate, and this only made her more curious. Over the course of the evening, while watching the two interact, she started to wonder if there was more between John and the roommate than met the eye.
Reading his mom's thoughts, John volunteered, "I know what you must be thinking, but I assure you, Julie and I are just roommates."
About a week later, Julie came to John and said, "Ever since your mother came to dinner, I can't find the beautiful silver gravy ladle. You don't suppose she took it, do you?"
John said, "Well, I doubt it, but I'll write her a letter just to be sure."
So he sat down and wrote, "Dear Mother, I'm not saying you 'did' take a gravy ladle from my house, and I'm not saying you 'did not' take a gravy ladle.But the fact remains that one has been missing ever since you were here for dinner."
Several days later, John received a letter from his mother which read, "Dear Son, I'm not saying that you 'do' sleep with Julie, and I'm not saying that you 'do not' sleep with Julie. But the fact remains that if she was sleeping in her own bed, she would have found the gravy ladle by now."
I only take from the best, the original: http://www.snopes.com/risque/caught/ladle.asp